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The present invention relates generally to wastewater treatment. More particularly, this invention pertains to a system and method of treating wastewater in a single impoundment by employing an internal permeable treatment container (or a xe2x80x9cpermeable containerxe2x80x9d). The permeable container may be made of any permeable material including, but not limited to, geotextile fabric, fabric, porous concrete, sintered metal, or metallic screen.
Companies, farms, and governmental entities (such as municipalities) routinely have or receive, and subsequently treat, wastewater for re-use or discharge, the treating being performed under numerous federal and state regulations. Although configurations of wastewater treatment systems can vary widely from system to system, such systems normally operate in several stages.
In a first stage (i.e. a xe2x80x9cpermeable stagexe2x80x9d), raw wastewater (influent) flows through a quiescent impoundment in which primary solids are allowed to settle to the bottom of the impoundment. In a second stage, the relatively solids-free wastewater then flows through a secondary treatment reactor where colloidal and soluble organic materials in the wastewater are used as a food source for a biological culture resident in the secondary treatment reactor, and the organic materials are thereby digested and converted to new cells and gaseous byproducts. This second stage may be performed aerobically or anaerobically. In aerobic treatment systems, the byproducts are new cells and carbon dioxide. In anaerobic treatment systems, the byproducts are new cells and other gaseous byproducts that may include methane, hydrogen sulfide, and nitrogen.
In a third stage, the wastewater and biological culture (biosolids) then flow through a final clarifier tank where the biosolids are allowed to separate, agglomerate, settle, and thicken. Solids-free wastewater may be discharged or undergo additional treatment. A portion of the biological cells may be returned to the secondary treatment reactor to maintain a desired mass for wastewater treatment. Excess biological solids and permeable solids may undergo additional treatment to reduce mass, reduce putrescible fraction, improve dewatering characteristics, or destroy pathogens. These solids are digested in either aerobic or anaerobic vessels. Digested solids may be then be dewatered, landfarmed, composted, incinerated or landfilled. Dewatering is typically accomplished using various means such as sand-drying beds, vacuum filters, or filter presses to filter in the water fraction from the biosolids.
The conventional wastewater treatment system as described above requires the use of three or more impoundments and a dewatering process. Each impoundment must be connected to at least one other impoundment by piping. Consequently, conventional wastewater treatment systems require substantial engineering design, construction expertise, high capital cost, and highly skilled operating personnel.
What is needed, then, is a system and method for completely treating wastewater and byproduct biosolids in a permeable container placed within a single impoundment.
This invention is a system and method that allows for the treating of wastewater within a single impoundment. Specifically, the invention is a two-part system that will contain wastewater during all of the stages of the wastewater treatment process (i.e., primary clarification, primary solids digestion, biological treatment of organics and nitrogenous compounds, final clarification, biological solids digestion, and solids dewatering). The two parts of the wastewater treatment system are a permeable container that holds the wastewater in contact with the biosolids while the wastewater is being treated, and an impoundment that holds the permeable container, its contents, and any wastewater that has already been treated. An important element of the invention is the permeable container, because it enables consolidation of multiple tanks and stages into one impoundment. This permeable container may be of any construction including, but not limited to, a woven geotextile fabric, a woven fabric, a woven synthetic fabric, a screen, or porous concrete. The permeable container is placed into the impoundment, which is a rigid container such as a tank or lagoon sufficient to completely house the permeable container and the wastewater. More than one permeable container may be housed in an impoundment.
In the method of the invention, untreated wastewater may be pumped or may flow via gravity directly into the permeable container. Air, oxygen, nutrients, or other additives may be added directly into the permeable container as well. The contents of the permeable container are completely mixed by either a recirculating pump, an aerator, or both. Biosolids grow and accumulate within the permeable container and on the container walls and provide for the following results: reduction of organic material, converting the material into new cells and gaseous byproducts; oxidation of nitrogenous compounds followed by the reduction of nitrates to nitrogen gas; and auto-oxidation of excess biological solids. The treated wastewater flows or is forced through the walls of the permeable container into the impoundment, from which it is removed by gravity or by pumping.
Eventually, the permeable container will reach the end of its useful life, as determined by deteriorating treated-wastewater quality over time. At the end of the permeable container""s useful life, the permeable container will need to be removed and recycled or replaced. To remove the permeable container from the impoundment, biosolids are digested and gravity-dewatered at the end of the system""s life cycle by stopping raw wastewater flow. Mixing or aeration continues for a predetermined period, then the impoundment is substantially drained of liquid, the permeable container will be allowed to drain more of its liquid contents, and the permeable container may be removed, where the remaining contents of the permeable container are allowed to dewater and desiccate.
Accordingly, it is an object of the invention to provide a system and method for treating wastewater and byproduct biosolids within a single impoundment.
It is a further object of the invention to provide a system and method for treating wastewater using a permeable material as a permeable container.
It is a further object of the invention to simplify the wastewater treatment process.
It is a further object of the invention to reduce wastewater treatment system construction cost.
It is a further object of the invention to have a wastewater treatment system that can be constructed in a short period of time.
It is a further object of the invention to reduce prerequisite skills, knowledge, and experience necessary to construct, operate, and maintain a wastewater treatment system.
It is a further object of the invention to be scalable -for any quantity of wastewater.
It is a further object of the invention to have a wastewater treatment system than can be operated in a limited land area.
In addition to the foregoing, further, objects, features, and advantages of the present invention should become more readily apparent to those skilled in the art upon a reading of the following detailed description in conjunction with the drawings, wherein there are shown and described illustrated embodiments of the invention.